Sorry if I have chosen a wrong topic for my question. I have exported GeoNames database for Germany. All administrative divisions are OK but there is no information about cities in ADM4. All PPL objects have blanks in their ADM2, ADM3, ADM4 fields so there is no way to determine in which ADM PPL object is located. I want to know if this information will be added in the future and what is the proirity of this task? Thank you in advance for answers.

I just spent a day or so researching this issue -- then came here and found this discussion. One of these days I'll get things in the right order.

By my calculations there are 8328 German records for which the admin level codes are incorrect. I also believe that the records to the ADM1 level are correct. At first I thought the problem was that "Landkreis" records are at the ADM3 level when they should be at ADM2 and the ADM4 under the Landkreis records should be at ADM3. But then I find that some German states use a "Regierungsbezirk" layer which really is the ADM2 that is above the "Landkreis" level. Note that not all states use this structure so for those states there is no ADM2 level. All in all the data appear to be correct. However this begs the question: Is the data modelled correctly?

Perhaps we should start a discussion about how to best model the data bases on usage. For the most part I think that, in most cases admin levels are used to start/restrict searches. So, for example, one might want to find all the lakes in Weld County, Colorado, USA and so start with that restriction. In a sense the admin records are used to traverse up and down a hierarchy.

Perhaps a structure that uses up and down pointers (a b-tree approach for the technically minded) might be in order here.

I'm going to bring this post back up again.
I've done some research on the Administrative Division stuff in Germany.

Currently only 5 (of 16) states have "Regierungsbezirke" - said "Regierungsbezirke" are ADM2 level entities in those states:
Baden-Württemberg
Bavaria (Bayern)
Hessen
North Rhine-Westphalia (Nordrhein-Westfalen)
Saxony (Sachsen) (the "Regierungsbezirke" are now called "Direktionsbezirke"; in the database, they are still called "Regierungsbezirke")

In these states ("Bundesländer") the "Landkreise" should consequently be ADM3 level.

In the remaining states there are no "Regierungsbezirke" or comparable entities; here the Landkreise (or districts) should be ADM2 level.
This, however, leads to the confusing situation that entities that are basically comparable (the "Landkreise") will be ADM2 level in some states and ADM3 level in others.
This problem could be solved by leaving blank the ADM2 level or omitting it in states without "Regierungsbezirke" and making the Landkreise ADM3 level subdivisions.

By now the situation is not very satisfying, because there is no way to add the Landkreis information to a dataset that is in an ADM1 level (Bundesland) that does not have any ADM2 children (Regierungsbezirke).